1. Field of the Invention
The invention relates to a device for guiding away cold-rolled tubes behind a cold-pilger rolling mill with intermittent feeding and/or rotating of the tube. The tube is diverted out of the rolling direction in a buffer zone between the rolling zone and a driver operating at a constant speed in order to compensate for the cyclically non-uniform rolling speed.
2. Discussion Of the Prior Art
From the generic document DE 31 46 284 C2, a process and a device are known for guiding away cold-rolled tubes of long length behind a rolling mill with a rolling stand that moves back and forth and has within it forcibly driven grooved rollers with intermittent feeding and/or rotating of the tube in the area of one or both dead center(s), whereby the alternating rotations are equally large in each rotation direction. The known process calls for the cyclically non-uniform feeding/exit speed of the rolled tube, which is typical of cold pilger rolling mills with rolling stands that move back and forth, to be changed into a constant run-out speed in a buffer zone while the tube is conducted by a drive apparatus operating at a constant speed at a distance from the rolling zone. The drive apparatus is located at such a distance that the torsional stresses in the tube do not exceed the yield strength of the tube.
The known solution is based on a known problem in cold pilger rolling mills, namely, that in the case of longer tube lengths, the entire tube length must continually be accelerated and braked during the cyclical feed, whereby the acceleration forces necessary for this must be produced by the forming process. These accelerative and decelerative forces are usually transmitted by the clamping chucks (clamping slots, run-in clamping chucks, and run-out clamping chucks) and, as applicable, an additionally present tube brake. Even in tubes of lengths starting at approximately 90 meters, accelerations of over 10 g occur, which increase as the tubes become longer and finally may lead to the tube moving forward in uncontrolled fashion in the rolling direction during its deceleration phase, i.e., to the occurrence of an unwanted feed. The deceleration forces which must be produced in order to arrest the tube depend, among other factors, on the mass of the finished tube to be decelerated and on the number of strokes of the cold pilger rolling mill.
Another problem is that it is necessary, particularly during the rolling of copper tubes, to reduce the number of strokes of the cold pilger rolling mill when the tube being rolled at a particular moment has left the first of the arresting elements, namely the clamping slots. When the tube has, in addition, left the run-in clamping chucks, the number of strokes must be reduced again. The higher the number of strokes during normal operation, the greater the effect this reduction in the number of strokes will have on the total achievable production of the cold pilger rolling mill. This is especially true when the nominal number of strokes is to be increased through other measures.
It has already been suggested in the generic document mentioned previously that, in order to limit the masses to be accelerated and decelerated, the length of the tube which is located behind the buffer zone existing between the rolling zone and the driver be dynamically decoupled from the remaining tube mass, so that only the mass of tube still remaining in the buffer zone needs to be cyclically moved. The design of the known solution calls for the tube to be diverted from the rolling plane following a straight run-out segment approximately 30 meters in length and to be introduced into the drive apparatus in a curvature of approximately 15 meters radius at a diversion of approximately 70 degrees.
In practice, it has been shown that a large diversion of this sort from the rolling axis leads, in almost all cases, to significant space problems which rule out the use of the known device.